The present invention relates to a novel process for preparing alkoxytriazolinones of the general formula 
and a novel hydrazinecarboxylic acid ester of the general formula 
which serves as intermediate in the preparation according to the invention of the alkoxytriazolinones. Alkoxytriazolinones are important intermediates for preparing agrochemically active compounds.
R1, R2 and R3 independently of one another are an optionally substituted straight-chain or branched C1-6-alkyl group. Methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl and its isomers and hexyl and its isomers may be mentioned by name. Moreover, R1 and R2 independently of one another may be optionally substituted aryl, arylalkyl or cycloalkyl. Aryl has preferably the meaning phenyl. Arylalkyl is preferably phenylalkyl, for example phenyl-C1-6-alkyl, and particularly preferably benzyl. Cycloalkyl is, in particular C3-6-cycloalkyl, preferably cyclohexyl. Suitable substituents of the alkyl groups, the aromatic compounds of the aryl function, or the cycloalkyl groups are, for example, halogen, amino, alkylamino, dialkylamino, alkoxy or hydroxyl, where alkyl, as above, is preferably C1-6-alkyl and alkoxy is preferably C1-6-alkoxy. Here and below, halogen is to be understood as meaning fluorine, chlorine, bromine or iodine. R1 is preferably methyl, propyl and phenyl, and particular preference is given to methyl and propyl. R2 is preferably methyl, benzyl and cyclohexyl. R3 is preferably methyl.
It was the object of the invention to provide an economical, industrially feasible process for preparing alkoxytriazolinones. This object is achieved by the process according to Patent Claim 1 and by the novel intermediate according to Patent Claim 10. According to the invention, in a first step, an iminocarbonic acid diester of the general formula 
in which R1 has the abovementioned meaning, is reacted, in the presence of a mineral acid and dissolved in water or in a mixture of water with a water-miscible polar organic solvent, with a carbazinic acid ester of the general formula 
in which R3 has the meaning mentioned, to give a hydrazinecarboxylic acid ester of the general formula 
in which R1 and R3 have the meanings mentioned.
Iminocarbonic acid diesters of the general formula II can be prepared according to EP-A 0 523 619 or according to Hantzsch (Chem. Ber., 1895, 28, 2470-2471). Carbazinic acid esters are customary organic chemicals for synthesis.
The mineral acid used can be hydrochloric acid, phosphoric acid or sulphuric acid. Hydrochloric acid is particularly suitable.
Water-miscible polar organic solvents are expediently straight-chain or branched alcohols having 1 to 6 C atoms. Methanol, ethanol, propanol, isopropanol, butanol, isobutanol or tert-butanol, pentanol and its isomers and also hexanol and its isomers may be mentioned by name.
The reaction of the first step is expediently carried out at a temperature from xe2x88x925 to 40xc2x0 C., advantageously at from 0 to 20xc2x0 C. The pH is expediently in a range from 3 to 10, advantageously in a range from 5 to 8. After a customary reaction time of from 30 min to 2 hours, the compound of the general formula IV, which has hitherto not been described in the literature, can be isolated by customary methods, such as, for example, extraction, or be employed directly, without isolation, for the second step. The intermediate (formula IV) is preferably isolated.
In a second step, the hydrazinecarboxylic acid ester according to the invention (formula IV) is reacted with an amine of the general formula
R2xe2x80x94NH2xe2x80x83xe2x80x83V
in which R2 has the meaning mentioned, in the presence of water, a polar organic solvent or mixtures thereof, to give the end product of the formula I. The reaction is preferably carried out in the presence of a polar organic solvent.
The polar organic solvents used are expediently straight-chain or branched alcohols having 1 to 6 C atoms. Methanol, ethanol, propanol, isopropanol, butanol, isobutanol or tert-butanol, pentanol and its isomers and also hexanol and its isomers may be mentioned by name. Particular preference is given to methanol.
The reaction of the second step is expediently carried out at a temperature of from 10 to 200xc2x0 C., advantageously from 20 to 100xc2x0 C.
The reaction of the second step is expediently carried out via an intermediate of the general formula 
in which R1, R2 and R3 have the meanings mentioned, which can, if appropriate, be isolated. The reaction of the second step is expediently carried out using an excess of the amine of the general formula V, based on the hydrazinecarboxylic acid ester of the general formula IV. The amine of the general formula V is preferably employed in a ratio of 1.1:1 to 30:1, particularly preferably in a ratio of from 2:1 to 20:1, based on the hydrazinecarboxylic acid ester of the general formula IV. Likewise expediently, the reaction of the second step can be carried out, after formation of the intermediate of the general formula VI, in the presence of a base. Suitable bases are alkali metal alkoxides, such as sodium methoxide or sodium ethoxide, and alkali metal hydroxides, such as sodium hydroxide or potassium hydroxide, in each case being optionally dissolved in the corresponding alcohol or in water.
After a customary reaction time of in total from 5 to 15 hours, the compound of the general formula I are obtained, and they can then be worked up by customary methods. Iminocarbonic acid diesters used as starting material for the preparation according to the invention of the alkoxytriazolinones can be prepared alternatively to the process as described in EP-A 0 523 619 and Hantzsch (Chem. Ber., 1895, 28, 2470-2471).
Here, an alcohol of the general formula
R1xe2x80x94OHxe2x80x83xe2x80x83VII
in which R1 has the meaning mentioned is, in a first step, reacted with an alkali metal to give the corresponding alkoxide.
The alcohol used can be a straight-chain or branched alcohol having 1 to 6 C atoms. Methanol, ethanol, propanol, isopropanol, butanol, isobutanol, tert-butanol, pentanol and its isomers and also hexanol and its isomers may be mentioned by name. Preference is given to using methanol. The alkali metal used can be sodium or potassium. Preference is given to using sodium. The reaction of the first step is expediently carried out at a temperature of from 10 to 80xc2x0 C., advantageously from 20 to 40xc2x0 C. In the second step, the alkoxide is reacted with a halocyanogen to give the end product of the formula II. The halocyanogen used is chlorocyanogen or bromocyanogen, preferably chlorocyanogen. The reaction of the second step is expediently carried out at a temperature from xe2x88x9220 to 20xc2x0 C., advantageously at from xe2x88x9210 to 5xc2x0 C. After a customary reaction time of from 1 to 2 hours, the compound of the general formula II can be isolated or be employed directly, without isolation, as starting material for the preparation according to the invention of the alkoxytriazolinones. The compound of the general formula II is preferably employed directly for the preparation according to the invention of the alkoxytriazolinones.